Electric high pressure discharge lamps



May 21, 1963 A. BAUER ELECTRIC HIGH PRESSURE DISCHARGE LAMPS 5Sheets-Sheet l Filed Aug. 11, 1960 INVENTOR Arnold Bauer M P ATTCENEY IMay 21, 1963 A. BAUER ELECTRIC HIGH PRESSURE DISCHARGE LAMPS 5Sheets-Sheet 2 Filed Aug. 11, 1960 INVENTOR Arnold Bauer M II? &'

ATTORNEY May 21, 1963 A. BAUER ELECTRIC HIGH PRESSURE DISCHARGE LAMPS 5Sheets-Sheet 3 Filed Aug. 11, 1960 Fig.5

T N E V N BY Arnold Bauer ATTORNE May 21, 1963 A. BAUER ELECTRIC HIGHPRESSURE DISCHARGE LAMPS 5 Sheets-Sheet 4 Filed Aug. 11, 1960 Fig. 7a

Fig. 8

INVENTOR Y Arnold Bauer M P W ATTORNEY May 21, 1963 A. BAUER ELECTRICHIGH PRESSURE DISCHARGE LAMPS 5 Sheets-Sheet 5 Filed Aug. 11, 1960 Fig.9

INVENTOR Arnold Bauer BY P ATTORNEY United States Patent ELECTRIC HIGHPRESSURE DISCHARGE LAMPS Arnold Bauer, Augsburg, Germany, assignor toPatent- Treuhand Gesellschaft fiir Electrische Gluhlampen NEBH, Munich,Germany Filed Aug. 11, 1960, Ser. No. 48,888 Claims priority,application Germany Aug. 14, 1959 25 Claims. (Cl. 313-113) Thisinvention relates to lamps, and more particularly to electrical highpressure discharge lamps for such purposes as moving picture projection.

Capacity concentrations aproaching 10 w./cm. as desirable for projectionlight sources, have already been achieved in electrode-stabilized highpressure lamps in which the discharge laces itself to a thin are burningbetween the electrodes and the stability of which depends considerablyon the condition of the electrode; but prior to this inventionwall-stabilized high pressure lamps have not been achieved.

The advantage of the wall stabilization consists in the are beingunlimited in its length, and consequently its potential demand, andtherefore the capacity and wattage of the lamp, can be increased simplyby extension of the arc.

The object of the invention is the creation of a onesided wallstabilized electric high pressure discharge lamp which, withoutartificial cooling, allows a wall charge of one thousand to fivethousand watts per square centimeter, and therefore a capacityconcentration of up to w./cm. and more.

According to the invention, at least two magnet poles of oppositepolarity are placed closely to the discharge are in such a way that,along the discharge course or at least that part of the discharge coursealong side of which the arc is to be concentrated, a non-homogeneousfield is created, formed of strongly bent field lines which areprimarily situated in areas vertical to the discharge axis. Preferablytwo magnetic pole shoes are so placed that their axes are in transverseposition to the axis of the discharge course and together form an angleof less than 180. According to the present invention, a flat or bentmetal wall is built in the discharge-enclosing envelope adjacent andimpervious to the are so that the bent magnetic field will limit the arefrom three directions and the said wall will limit it in the fourthdirection.

In comparison to quartz glass, the metal wall provided by this inventionhas the advantage of a wall charge increased by wall dimensions andconsequently allows, without additional cooling, a far higher eiliciencyconcentration than all devices so far known.

A further advanatge of the metal wall is that it can reach a highertemperature than quartz glass. Consequently the difference intemperature between the hot arc gases and the stabilizing wall is lower,which will diminish chances for loss of heat by thermal conduction. Towithstand high temperatures, the metallic wall preferably consists oftungsten or molybdenum, free from impurities, such as thorium, whichmight decrease exit action.

Considering their good electrical conductivity and absence of lightfiltration, metal walls have so far not been used for stabilization ofhigh pressure arcs. According to this invention, however, the arc isstabilized on only one side by a metal wall and from all the other threedirections is compressed by a magnetic field. Preferably, the metal wallalso constitutes a light reflector having a shape comparable to that ofa concave or recessed mirror. Increased reflection of the metal surfacecan be achieved through polishing, or .by coating with, for example,rhodium or platinum. The coating will simultaneously serve to increaseexit action.

It would be normal expectation that an arc stabilization by anelectrically good-conducting metal wall Would include the danger of thearc being short-circuited by the wall. However, I have discovered that arelatively cold gas layer of high electrical resistance will formbetween the arc and the metal wall, which, together with the potentialincrease of the metal surface will avoid short circuit of the arc aslong as the voltage drop of the arc alongside the metal wall remainsbelow a certain critical value, namely twenty to thirty volts. Themagnetic field energy used in conjunction with the aforesaid selectedmetal for the wall and temperature of the wall, determines theparticular value within the permissible critical range of twenty tothirty volts. In the high pressure lamps of the present invention, thevoltage intensity is usually of the higher amount, so that it becomesdesirable or necessary to construct the wall of individual electricallyisolated parts. The metal wall may reach high temperatures even close tobut less than the melting point of tungsten or molybdenum which is over2000" C., but by virtue of the said cold gas layer, no cooling of anykind becomes necessary. It is within the scope of the invention,however, to coat the wall serving the arc stabilization with a highmelting heat insulator, which makes it possible to utilize a one-piecewall instead of requiring it to be sectioned into individually isolatedparts. By preference high melting heat insulator components are usedwhich simultaneously have high optic reflective capacity, such asaluminum oxide, beryllium oxide or silicon dioxide, available in layersof a thickness less than one millimeter, preferably one to ten microns.In order to intensify heat radiation, the parts of the metallic wallwhich do not face the discharge are, may also receive an appropriatecoating of, for example, tantalum carbide or carbon.

Especially when the magnet poles are placed inside the discharge tank orenvelope, not only a straight axial burning arc may be laced in, but itis also possible to lead the arc, of the order provided by theinvention, into a certain course, such as a U-course or a zigzag course.This makes it possible to provide a better adaptation to the screen sizeof projectors and a more even illumination of the picture than has sofar been achieved with usual high pressure lamps, without particularprovisions, such as comb condenser.

For magnet poles placed inside the discharge envelope, it is morepractical to use components with a higher Curie point, such as cobalt oran alloy of cobalt and iron, which will permit a higher operatingtemperature. The magnetic flux circulating the pole shoes can be guidedthrough a magnet core placed outside the lamp envelope; also themagnetic circuit may be completed by a core placed inside the envelope;or if desired, two individual magnets may be provided. In dischargelamps run by direct current, permanent magnets may be used supplementaryto the electro-magnets. Both with direct current and with alternatingcurrent, it is practical to include the electro magnet in the dischargecircuit. To achieve special discharge courses, more than two pole shoesmay be provided to create the non-homogeneous field, or in addition totwo primary magnet poles two secondary poles may be provided andarranged with their field functioning oppositely to the magnetic fieldof the primary poles, both fields being in the region of the dischargearc and thereby increasing its non-homogeneity.

The invented lamps, presented herein, combine the advantages of the Wallstabilization with those of the electrode stabilization. An evenlyconcentrated, strongly burning arc is produced by the invention; thelength of the arc can be increased and the voltage may be freely chosenwithin a Wide range. By the invention, increased other glass.

Voltage and decreased lamp currents are achieved as compared to priorart electrode stabilized lamps of equal capacity. Furthermore theelectrodes of the lamps may 'be reduced over prior art construction, sothat the lamps of the present invention are well adapted to serve theimpulse industry which is of growing importance to larger filmprojectors.

The invention may be well applied to rare-gas high pressure lamps, forinstance to lamps filled with xenon. The envelopes may be of desiredshape, such as globular or elongated and of desired material such asquartz or It is also within the scope of the invention to utilize it asa metal vapor high pressure lamp filled, t or example, mercury vaporwith which may be included in addition to the metal vapor a permanentignition gas to a considerable degree, such as xenon, crypton, argon orother molecular gas the partial pressure of which may be, duringoperation, either lower or higher than the metal vapor pressure.

Referring to the accompanying drawings, in which like numerals ofreference indicate similar parts throughout the several views;

FIGURE 1 shows an especially simple example of lamp embodying theprinciple comprising the basis of the invention;

FIGURES 2 and 2a show a construction by which a winding-line arc isobtained;

FIGURE 3 is a cross section of a high pressure lamp according to theinvention with a straight axis discharge;

FIGURES 3a and 3b are longitudinal sections taken on lines 3a--3a andlib-3b respectively of FIG. 3;

FIGURE 4 is a partial View of a lamp showing the coupling of a magnetcore with pole shoes placed inside the lamp envelope;

FIGURE 5 shows the application of the invention to a high pressure lampwith'a metal envelope;

FIGURE 5a shows the electrodes of the lamp of FIG. 5;

FIGURE 6 is a projection lamp with built-in reflector;

FIGURE 7 is a longitudinal section of a high pressure discharge lamp themetallic wall of which is coated with a high melting heat insulator;

FIGURE 7a is a sectional view on line 7a-7a of FIG. 7;

FIGURE 8 is a longitudinal section of a high pressure discharge lampwitha U-form arc;

FIGURE 8a is a perspective view of the metallic wall and magnet of thelamp of FIG. 8;

FIGURE 9 is an elevation, partly in section, of a high pressuredischarge lamp providing a recessed reflective wall laminated indirection of the arc; and

FIGURE 9a is a lamp in section showing primary and secondary magnetsassociated therewith.

In the specific embodiment of the invention illustrated, and referringinitially to FIGURE 1, the reference numeral 1 designates two magnetpole shoes which are so placed inside a discharge tank or envelope thatthey create a non-homogeneous field which is primarily composed of twostrongly bent field lines 2. Those field or fiux lines are mainlylocated in the area designated by the direction of the two-pole shoes.This non-homogeneous magnetic field develops a Lorentz power afiectingthe discharge are 3 from three directions, concentrating and stabilizingit magnetically, and forcing it against the metallic wall 4 which is atthe fourth side.

By an arrangement shown in FIGURE 2, it is possible to force a highpressure am into a winding-line or Zigzag wave 5. The length of such anarc exceeds by far the length of straight line arcs normally obtained inthe prior art by electrode-stabilized arcs. The magnet poles 6 "shown inFIGURE 2a create the Lorentz field indicated A rare gas high pressurelamp embodying the inven- '29 at a location remote from the arc.

tion may, according to FIGURES 3, 3a and 3b, provide an envelope 9 ofquartz glass having therein two primary metal electrodes 10 as well asan ignition secondary electrode 11 which is coupled with one of theprimary electrodes. The are ignites at 12 (FIG. 3) where the distancebetween ignition electrode 11 to the primary electrode is the shortest.Assisted by the non-homogeneous magnetic field, the arc is blown rapidlyinto the straight axis operating position. Two magnets 13 of cobalt oralloy thereof have poles of opposite polarity located adjacent to a metal wall '14 for establishing a field at three sides of an arc (with thewall at the fourth side) for effecting the stabilizing and lacing of theare passing proximate to said wall, pressing the arc magneticallyagainst said wall. As shown, said wall 14 consists of individualtungsten slats that have been smoothed flat on both sides of their tips,and consequently enables the magnet poles to be located proximate to theflats, and, as explained above, affords protection against hot gases.The individual slats composing said wall 14 are sealed into the stem orbase 15 of the discharge lamp, and are isolated thereby bothindividually as well as from the electrodes 10. The thermal energycreated by the discharge and supplied to the wolframite slats of wall 14and to the operating electrodes 10 can be disposed of without additionalcooling devices. The two magnets 13 are fixed to the center one of slats14 by means of a bracket 16 of non-magnetic material such asnon-magnetic steel.

It may be here noted that, as shown in FIGURE 4, instead of havingpermanent magnets inside the envelope, pole shoes 17a may be locatedinside the envelope 9 and the magnet core 17 located outside theenvelope in inductive relation to said shoes for obtaining magneticcoupling therewith.

FIGURES 5 and 5a show a high pressure lamphaving an envelope the majorportion of which is metal and is of a character fit for projectionpurposes. The lamp produces a straight arc which is pushed against theback wall 19 by means of the non-homogeneous. magnetic field produced bymagnetic pole shoes 18. The major portion of the envelope is made ofnonmagnetic metal, such as brass, and at one end thereof is providedwith a screen 21 made of quartz glass or other suitable glass, sealed tothe metal portion by lead rings 22. The filling may consist of xenonwhich in operationreaches a pressure of about twenty-five atmospheres.The light arc 7 may, as a specific example have a length of tenmillimeters and a diameter of two millimeters with an applied currentflector 25 at one end of the lamp body 26, and the metal wall 27 bywhich the arc is stabilized as the discharge is forced thereagainst, isso curved that the light is received by the condensing reflector in itsfull intensity and reflected on a glass screen 29 at the opposite end ofthe envelope from said reflector. An advantage of this construction isthe adaptability to use of a small lamp screen Remainders of foreigngases, especially oxygen, are not easily removable from metal lamps.Consequently zirconium or titanium are therefore usually employed withthe metal lamps disclosed herein.

The lamp according to FIGURE 7 has an envelope 30 of quartz glass intowhich have been scaled a cathode 31, an anode 3-2, and an ignitionelectrode 33. v

The lamp as disclosed in FIGURE 7 has a quartz glass envelope 30 intowhich have been sealed a cathode 31,

an anode 32, and an ignition electrode 33. The metallic stabilizing wall34 is formed with a frontal surface of a tungsten slat 35 sealed intothe envelope. Lateral clearances are provided in the edges of the slat35 behind said wall 34 for receiving two magnet poles 36 in closeproximity to said wall. The frontal surface of said wall 34 is providedwith a coating 37 of aluminum oxide which has a thickness of fivemicrons, and developed into a reflector. The three remaining sides ofthe slat not facing the discharge arc, and possibly also parts of themagnets 36, are provided with a film 3 8 of tantalum carbide.

The lamp shown in FIGURES 8 and 8a is provided with two horn-shapedelectrodes 39 and with a stabilizing wall 40 consisting of a tungsten ormolybdenum sheet on which is carried a horse-shoe magnet 41 and anothermagnet 42 of bar shape lying between the legs of the horse-shoe magnet41. The surface of the wall 40 facing the discharge between theelectrodes is coated with a layer 43 of aluminum oxide which has a tenmicron thickness. This discharge lamp ignites where the two horn-shapedelectrodes 39 have minimum distance between them, and is then, under thepressure of the magnetic field of the current leads and electrodes,driven to the electrode points, and by the field supplied by magnets 41and 42 forced to deploy into the U-shape are 44 indicated in FIGURE 8.

Considering now the showing in FIGURES 9 and 9a of a rare gas highpressure lamp, it may be said briefly that the same comprises a quartzglass envelope of the same order as in FIGURE 7 and here identified byreference numeral 45. Sealed in said envelope are aligned anode 46 andcathode 47, and directed laterally thereof and at the spacingtherebetween are shown five tungsten slats 48 also sealed in theenvelope. Said slats are isolated from each other and their forward endsproximate to the path of the are are recessed in V-shape and thereconstitute stabilizing wall for the arc. The non-homogeneous magneticfield by which the arc is pressed toward said wall as indicated at 49 iscreated by a primary pair of magnets 50 placed outside the envelope andthe nonhomogeneity is increased by addition of a secondary pair ofmagnets 51 also outside the envelope. The polarity direction of thesecondary pair of magnets is in reverse of the polarity direction of theprimary pair of magnets. These exterior magnets may be either or bothelectro magnets or permanent magnets.

I claim:

1. An electric high pressure discharge lamp having electrodes and anenvelope therefor filled with gas selected from the group of rare gases,metal vapors and mixtures thereof will magnetic lacing and stabilizingof the discharge arc; the characteristic being that close to thedischarge arc at least two magnet poles are so placed that, alongsidethe discharge course for at least that particullar part of the dischargecourse along which the are discharge is to be laced and compressed, anon-homogeneous magnetic field is composed of strongly bent field linesessentially situated in areas traversing the discharge, said lamp beingfurther characterized by the fact that Within the envelope is provided ametallic wall isolated electrically from the electrodes and so placedthat the arc, laced-in magnetically from three sides, is magneticallypressed toward said wall.

2. An electric high pressure discharge lamp in acordance with claim 1,characterized by the fact that the metallic wall is a material of highmelting point selected from the group consisting of tungsten andmolybdenum.

3. An electric high pressure discharge lamp in accordance with claim 1,characterized by the fact that the surface of the metallic wall facingaway from the discharge are has a coating which increases its radiatingpower.

4. An electric high pressure discharge lamp in accordance with claim 1,characterized by the fact that the metalance with claim 1, characterized'by the fact that the metallic wall is composed of frontal elementscomprising rectangular tungsten slats.

7. An electric high pressure discharge lamp in accordance with claim 1,characterized by the fact that the metallic wall comprises a one-pieceelement.

8. An electric high pressure discharge lamp in accordance with claim 1,characterized by the fact that the metallic wall comprises a sheetingselected from the group consisting of tungsten and molybdenum and saidsheeting has a thickness of one half to three millimeters.

9. An electric high pressure discharge lamp in accordance with claim 1,characterized by the surface of the metallic wall facing the dischargearc comprising a coating of a high melting electrically isolatingmaterial less than one millimeter thick.

10. An electric high pressure discharge lamp in accordance with claim 1,characterized by the metallic wall facing the discharge are comprising acoating of electrically isolating material of a high melting oxideselected from the group of aluminum oxide, berylium oxide and silicondioxide.

11. An electric high pressure discharge lamp in accordance with claim 1,characterized by said metallic wall facing the discharge are comprisinga coating having a thickness between one and ten microns.

12. An electric high pressure discharge lamp in accordance with claim 1,characterized by the fact that the nonhomogeneous field is created bytwo magnetic poles the axes whereof are transverse to the axis of thecourse of the discharge are and together form an angle of less than 13.An electric high pressure discharge lamp in accordance with claim 1,characterized by the fact that there are two primary magnet poles andtwo secondary magnet poles situated to produce a field opposing themagnet field of the primary poles at the location of the discharge arefor increasing the non-homogeneity of the eifective magnetic field.

14. An electric high pressure discharge lamp in accordance with claim 1,characterized by the magnets being permanent magnets.

15. An electric high pressure discharge lamp in accordance with claim 1,characterized by the magnets being electro-magnets.

16. An electric high pressure discharge lamp in accordance with claim 1,characterized by the fact that the magnet is an electro-magnet andreceives its power from the lamp current.

17. An electric high pressure discharge lamp in accordance with claim 1,characterized by the fact that the nonhomogeneous magnet field iscreated by at least two magnet poles located internally of the envelope.

18. An electric high pressure discharge lamp in accordance with claim 1,characterized by provision of pole shoes internal to the envelope andexternal magnets in ductively coupled to said pole shoes.

19. An electric high pressure discharge lamp in accordance with claim 1,characterized by the fact that said field is created by poles locatedinternally of the envelope with said poles composed of magnetic materialwith a high Curie-point and composed at least in part of cobalt.

20. An electric high pressure discharge lamp in accordance with claim 1,characterized by provision of magnetic poles alternating north and southpolarity along the discharge course for forcing the are into awinding-line Wave. at

21. An electric high pressure discharge lamp in accordance with claim 1,characterized by a horseshoe magnet with a bar magnet between the legsthereof located behind the metallic wall at the side thereof facing awayfrom the discharge arc forforcing the are into a U-shaped course.

22. An electric high pressure discharge lamp in accordance with claim 1,characterized by at least two magnet poles located outside the envelope.

23. An electric high pressure discharge lamp in accordance with claim'lwherein the envelope consists of quartz glass and the electrodescomprise an anode, a cathode lope comprises a non-magnetic metal bodyhaving a 20 vacuum-tight screen at one part thereof, and wherein themetallic wall within the envelope toward which the arc is forced has theshape of a concave mirror for reflecting the light of the arc onto saidscreen.

25. An electric high pressure discharge lamp in accordance with claim 1,characterized by the fact that the envelope consists of non-magneticmetal body having a vacuum-tight screen inserted into the metal, saidbody having a part of its interior providing a condensing reflector, themetallic wall within the envelope toward which the arc is forced alsobeing constituted as a mirror arranged to direct light of the arc tosaid condensing reflector, and said condensing reflector arranged toreflect the light in full intensity to said screen.

References Cited in the file of this patent UNITED STATES PATENTS2,009,555 Mathiesen' July 30, 1935 FOREIGN PATENTS 886,708 Germany Aug.17, 1953

1. AN ELECTRIC HIGH PRESSURE DISCHARGE LAMP HAVING ELECTRODES AND ANENVELOPE THEREFOR FILLED WITH GAS SELECTED FROM THE GROUP OF RARE GASES,METAL VAPORS AND MIXTURES THEREOF WILL MAGNETIC LACING AND STABILIZINGOF THE DISCHARGE ARC; THE CHARACTERISTIC BEING THAT CLOSE TO THEDISCHARGE ARC AT LEAST TWO MAGNET POLES ARE SO PLACED THAT, ALONGSIDETHE DISCHARGE COURSE FOR AT LEAST THAT PARTICULLAR PART OF THE DISCHARGECOURSE ALONG WHICH THE ARC DISCHARGE IS TO BE LACED AND COMPRESSED, ANON-HOMOGENEOUS MAGNETIC FIELD IS COMPOSED OF STRONGLY BENT FIELD LINESESSENTIALLY SITUATED IN AREAS TRAVERSING THE DISCHARGE, SAID